1. Technical Field
The present invention relates to a light source unit and a projector and, more specifically, to a technology of a light source unit having a reflector.
2. Related Art
In a lamp used as a light source of a projector, for example, in a discharge lamp such as an extra-high pressure mercury lamp, a reflector (reflecting mirror) configured to reflect light emitted from an arc tube is employed. In the related art, a configuration of the light source unit for enhancing usage efficiency of light emitted from the arc tube is proposed in order to obtain bright images efficiently using the projector. For example, a technology in which a secondary reflector which covers part of the arc tube is provided separately from the reflector as a primary reflector is proposed (see Japanese Patent No. 3350003, for example). Light reflected from the secondary reflector passes through the arc tube, then falls on the primary reflector, and then is reflected therefrom toward the front. Accordingly, reduction in thickness of the light source unit is achieved while allowing the light emitted from the arc tube to proceed efficiently to an optical system which uses the light from the light source unit.
Japanese Patent No. 3350003 is an example of the related art.
The lamp used in the projector is heated to high temperatures because most part of supplied electric energy is transformed to heat, and thus needs to be cooled down by a cooling wind or the like. In the case of the configuration in which the secondary reflector is provided, a portion of the surface of a light-emitting portion covered with the secondary reflector is difficult to be cooled down. In this case, the portion of the surface of the light-emitting portion covered with the secondary reflector and other portions have different thermal radiation properties. Therefore, there arises a problem of difficulty in adjusting the temperature of the arc tube appropriately. As regards the portion of the arc tube which is not sufficiently cooled down, a transparent member which constitutes the arc tube may become opaque because of crystallization caused by heat. Provision of a blower or a fan duct is conceivable for cooling down the arc tube. However, problems such as complication of the structure and noise generation by the blower may arise.